Problem: How many significant figures does $074390$ have?
Solution: Identify the non-zero digits and any zeros between them. These are all significant. $0{7439}0$ Leading zeros are not significant. $\color{orange}{0}{7439}0$ Since there is no decimal, trailing zeros are not significant. $\color{orange}{0}{7439}\color{orange}{0}$ Counting all the significant digits gives us 4.